下调Skp2表达诱导乳腺癌MCF-7细胞凋亡

目的 探讨在乳腺癌细胞系MCF-7中下调S期激酶相关蛋白(Skp2)表达诱导细胞凋亡及其机制。方法 应用RNAi方法在体外下调乳腺癌细胞系MCF-7中Skp2的表达水平,48小时后表阿霉素处理细胞,TUNEL和Hoechst 33258染色检测凋亡,Western Blot检测细胞周期调控相关因子及凋亡相关蛋白表达情况,研究其机制。结果 下调MCF-7中Skp2表达水平后,乳腺癌细胞凋亡增加。下调Skp2使p27、p21和CyclinE蛋白表达水平升高。表阿霉素处理MCF-7细胞后,Skp2蛋白水平下调。Skp2 siRNA与表阿霉素有协同诱导凋亡的作用,p53蛋白水平升高。结论 p27、p21和CyclinE在通过下调Skp2诱导的凋亡中发挥作用。Skp2 siRNA和表阿霉素协同诱导细胞凋亡,与p53依赖的凋亡途径有关。Skp2可能是乳腺癌治疗的靶点。     

ING4基因表达对乳腺癌细胞生长抑制作用的研究

目的：研究人ING4基因对乳腺癌细胞MCF-7的生长抑制作用。方法：通过实时荧光定量-PCR（real-time fluorogentic quantitative-PCR，RFQ-PCR）检测3种乳腺癌细胞株中ING4 mRNA的表达水平；ING4基因的表达质粒转染MCF-7细胞；MTT法和FCM法检测ING4基因对MCFM细胞增殖的影响；Annexin-V／PI双染法观察细胞凋亡情况；RT-PCR法分析转染／NG4后p53、p21及bax基因的转录表达情况。结果：在3种乳腺癌细胞MCF-7、MDA-MB-435和MDA-MB-231中ING4的表达均明显低于正常乳腺组织。转染ING4表达载体的MCF-7细胞较对照组细胞生长速度减慢（P〈0．05）；细胞周期中G1期比例增加，S期比例减少；细胞凋亡率升高。p53的表达未见明显变化，而p21和bax表达显著上调。结论：ING4与乳腺癌的发生发展具有一定相关性；高表达ING4基因能够抑制人乳腺癌细胞MCF-7的生长。     

青蒿琥酯对人乳腺癌MCF-7细胞裸鼠移植瘤的作用及IGF—IR的影响

[目的]观察青蒿琥酯对人乳腺癌MCF-7裸鼠移植瘤生长的作用，并探讨其抑制肿瘤的机制。[方法]建立人乳腺癌MCF-7裸鼠移植瘤模型，给予不同剂量青蒿琥酯治疗并观察其对移植瘤的抑制作用；电镜观察移植瘤细胞形态学改变；流式细胞术检测细胞凋亡率和细胞周期的变化：免疫组化检测移植瘤细胞p53、bcl-2、bax和caspase-3的表达情况，分析它们之间的相关性；Westernblot检测IGF—IR蛋白的表达：[结果]给药12d后，低剂量、高剂量青蒿琥酯组、CTX组和联合给药组抑瘤率分别为（24．39±10．20）％、（40．24±7．02）％、（57．01±5．84）％和（68．29±5．1）％；青蒿琥酯使肿瘤细胞阻滞于G0／G1期而使S期细胞减少；在青蒿琥酯组中，bcl-2的蛋白表达量明显下降，bax、caspase-3蛋白表达上调，p53蛋白表达量与对照组比较无差异：bcl-2／bax及bcl-2／caspase-3表达均呈负相关．IGF-IR蛋白表达下调。[结论]青蒿琥酯可显著抑制乳腺癌MCF-7细胞裸鼠移植瘤的生长，其机制可能与其影响细胞凋亡相关蛋白、诱导凋广、抑制细胞增殖有关．     

丁酸钠对人乳腺癌细胞株MCF-7细胞增殖及p27^kip1蛋白表达影响的研究

目的：通过观察组蛋白去乙酰化酶抑制剂（histon—deacetylase inhibitors，HDACIs）丁酸钠（sodium butyrate，NaB）对人乳腺癌细胞株MCF-7细胞的增殖影响以及p27^kip1蛋白表达改变，探讨NaB调控乳腺癌细胞增殖的分子机制。方法：乳腺癌MCF-7细胞经不同浓度NaB作用后，相差显微镜观察细胞形态变化和细胞增殖情况，流式细胞仪分析细胞周期分布，免疫组化检测p27^kip1蛋白表达。结果：NaB对MCF-7细胞有显著的增殖抑制作用，呈时间剂量依赖性，处理后的MCF-7细胞出现凋亡形态变化；细胞周期阻滞于（G0／G1期，NaB2 mmol／L组G0／G1，期达（62．2±2．2）％，4mmol／L组G0/G1，期达（78．1±3．8）％，空白组G0／C0期达（53．1±2．4）％，P〈0．05；p27蛋白表达水平上调。结论：NaB可抑制乳腺癌细胞的生长，该作用可能与p27蛋白表达增加有关。     

PIN1 反义核酸对乳腺癌MCF-7 细胞增殖及周期的影响

 目的 本研究利用PIN1反义核酸阻断乳腺癌MCF-7细胞中PIN1表达，观察其对增殖及周期的影响。方法 构建PIN1反义核酸真核表达质粒pPINlas，用脂质体转染法将重组质粒转染MCF-7细胞，G418筛选稳定表达重组质粒的克隆，RT-PCR检测PIN1基因表达水平，Western blot检测PIN1蛋白的表达，MTT检测细胞增殖状况，流式细胞术检测细胞周期。结果 稳定表达PIN1反义核酸的MCF-7细胞内PIN1基因表达在mRNA水平和蛋白水平都显著降低；MTT实验显示MCF-7PINas细胞的增殖速度较MCF-7细胞明显减慢（P〈0．05），但FCM显示MCF-7PINas细胞和MCF-7细胞的周期分布差异无统计学意义（P〉0．05）。结论 阻断PIN1可以显著抑制乳腺癌MCF-7细胞的增殖活性，提示PIN1可能成为乳腺癌基因治疗的新的靶点。     

丹酚酸乙对乳腺癌MCF-7细胞的生长抑制及诱导凋亡研究

[目的]观察丹酚酸乙对乳腺癌MCF-7细胞的生长抑制及诱导凋亡作用。[方法]MTT法观察丹酚酸乙对体外培养MCF-7细胞的增殖抑制作用;Hoechst33258荧光染色法观察细胞凋亡的形态学变化;流式细胞仪检测丹酚酸乙作用于MCF-7细胞48h后细胞凋亡率和细胞周期的变化;Western Blot检测caspase-3蛋白表达的变化。[结果]丹酚酸乙能明显抑制MCF-7细胞的生长,呈剂量和时间依赖性;荧光染色结果显示,丹酚酸乙与MCF-7细胞共培养24、48和72h后,细胞呈现明显的核固缩、碎裂以及凋亡小体形成等细胞凋亡现象;流式细胞仪检测结果显示,不同浓度的丹酚酸乙处理MCF-7细胞48h后,细胞凋亡率和S期细胞的比例逐渐升高;Western Blot显示,随着丹酚酸乙浓度的增加,MCF-7细胞caspase-3蛋白表达水平逐渐升高。[结论]丹酚酸乙对MCF-7细胞具有明显的生长抑制和促凋亡作用,这种作用可能与上调caspase-3表达以及阻滞细胞于S期有关。     

5-氮杂-2’-脱氧胞苷对多药耐药MCF-7/ADR和KBV/200细胞增殖及细胞周期影响作用机制的研究

目的:探讨5-氮杂-2’-脱氧胞苷(5-aza-2’-deoxycytidine,5-Aza-dC)对肿瘤多药耐药细胞生长抑制率、细胞周期的影响及可能的作用机制。方法:采用MTT法检测5-Aza-dC对人乳腺癌耐药细胞株MCF-7/ADR、口腔表皮癌多药耐药细胞KBV/200及其相应的亲本敏感MCF-7和KB细胞的生长抑制率;FCM法检测不同浓度5-Aza-dC(1、5和10μmol/L)作用72h及5-Aza-dC(10μmol/L)作用24、48和72h后,各细胞周期分布的变化;分别采用实时荧光定量-PCR及蛋白质印迹法检测细胞周期相关蛋白cyclin A、cyclin E和p21waf1/cip1mRNA及蛋白的表达情况。结果:5-Aza-dC对耐药细胞株MCF-7/ADR及KBV/200均呈现明显的生长抑制作用,细胞周期被阻滞在G2/M期,并呈时间及剂量依赖性;细胞周期相关蛋白cyclin A、cyclin E和p21waf1/cip1mRNA及蛋白的表达均上调。结论:5-Aza-dC可以通过使MCF-7/ADR及KBV/200细胞的细胞周期被阻滞在G2/M期,从而抑制肿瘤多药耐药细胞的增殖;其作用机制可能与上调细胞周期相关蛋白cyclin A、cyclin E和p21waf1/cip1的表达有关。     

长链非编码RNA LINC01001 在乳腺癌中的表达及其对MCF-7细胞增殖的影响

目的：探讨长链非编码RNA LINC01001 在乳腺癌组织中的表达及其对乳腺癌MCF-7 细胞增殖能力的影响。方法：筛选2016 年3 月至2017 年6 月于湖北医药学院附属人民医院甲状腺乳腺外科行手术切除的乳腺癌患者癌及癌旁组织12 例,qRTPCR检测乳腺癌组织及癌旁组织LINC01001 的相对表达量;通过重组质粒在人乳腺癌MCF-7 细胞中过表达LINC01001,采用流式细胞术和MTT 法检测过表达LINC01001 后MCF-7 细胞周期分布和增殖能力变化。qRT-PCR 检测miR-485-5p 和CDKN1A mRNA的表达变化,Western blotting 检测CDKN1A、CDK4、CDK6 和Cyclin D1 蛋白表达变化。结果：LINC01001 在乳腺癌组织中表达水平低于对应的癌旁组织（P<0.01）。LINC01001 重组质粒转染MCF-7 细胞后可显著抑制细胞周期进展（P<0.05）,抑制细胞的增殖能力（P<0.05）。过表达LINC01001 后,MCF-7 细胞的miR-485-5p 的表达水平降低（P<0.01）,CDKN1A mRNA表达水平升高（P<0.01）;可促进CDKN1A蛋白的表达和抑制CDK4、CDK6 和Cyclin D1 蛋白的表达。结论：LINC01001 在乳腺癌组织中表达降低,其可能通过下调miR-485-5p 的表达上调CDKN1A的表达来抑制乳腺癌MCF-7 细胞的增殖能力,为lncRNA 的临床应用提供实验基础。     

丙戊酸钠对人宫颈癌细胞增殖和细胞周期的影响

[目的]研究组蛋白去乙酰化酶抑制剂丙戊酸钠对人宫颈癌Hela和Siha细胞株增殖和细胞周期的影响。[方法]用不同浓度丙戊酸钠分别作用Hela和Siha细胞，MTT法测生长抑制率，流式细胞仪检测细胞周期，RT—PCR和Western blot检测p21^WAF1/CIP1 mRNA和蛋白改变。[结果]丙戊酸钠对宫颈癌Hela和Siha细胞生长抑制呈剂量依赖性；丙戊酸钠使Hela和Siha细胞阻滞于G0／G1期；丙戊酸钠上调p21^WAF1/CIP1 mRNA和蛋白表达。[结论]丙戊酸钠能上调p21^WAF1/CIP1表达，促使细胞阻滞于G0／G1期,从而抑制宫颈癌Hela和Siha细胞生长。     

p21在乳腺癌化疗中对表柔比星的增敏性及其作用机制的研究

背景与目的:p21是一种重要的细胞周期负性调控因子,目前对其在乳腺癌化疗过程中的作用尚不明确.本课题旨在观察将p21基因转染乳腺癌细胞后,对表柔比星敏感性的改变,以探讨新的表柔比星耐药可能的机制.方法:构建表达载体pEGFP-p21,采用脂质体转染法转入乳腺癌细胞株MCF-7中,筛选稳定表达p21的克隆;应用实时荧光定量PCR法检测转染组细胞中p21 mRNA的表达,流式细胞术和Hoechst33342荧光染色法分析细胞周期分布和凋亡变化;应用MTT法检测p21基因转染前后MCF-7细胞对表柔比星敏感性的变化,实时荧光定量PCR法(real-time fluorogent quantitative PCR,RFQ-PCR)观察survivin mRNA水平的变化.结果:pEGFP-p21载体转染MCF-7细胞后,MCF-7细胞中p21 mRNA的表达量明显增高,是空白对照组的155倍;转染后的细胞被阻滞于G0/G1期,但实验组与空白对照组相比,凋亡率改变的差异无统计学意义(P>0.05);表柔比星与p21基因转染联合作用时,p21可促进表柔比星对MCF-7细胞的杀伤作用,且细胞的抑制随作用时间的增加而增强,同时伴有survivin mRNA表达的降低,与表柔比星单独作用相比,差异有统计学意义(P<0.05).结论:p21基因能增强MCF-7细胞对表柔比星的敏感性,其作用可能是通过使细胞周期发生G0/G1期阻滞及下调survivin的表达来实现的.     

缺氧对人乳腺癌MCF-7细胞miRNA-21表达的影响及与细胞增殖和凋亡的关系

[目的]观察缺氧环境下人乳腺癌MCF-7细胞增殖及凋亡的情况,初步探讨缺氧对miRNA-21表达的影响及其与细胞增殖、凋亡的关系。[方法]CoCl2人工模拟缺氧环境,四甲基偶氮唑蓝比色法（MTT）检测缺氧环境下细胞增殖状况,流式细胞仪检测细胞的凋亡率．实时荧光聚合酶链反应（RT—PCR）测定不同缺氧程度下HIF-1α 和miRNA-21表达水平的变化。[结果]与常氧对照组相比较,CoCl2处理组的细胞明显受到抑制,但100、200μmol／LCoCl2处理组的细胞在一定时间内仍增殖,抑制率随缺氧时间和药物浓度增加而上升。流式细胞仪检测结果显示,CoCl2处理组细胞凋亡率高于对照组（P〈0．05）。RT-PCR检测显不,200、400μmol／L的CoCl2处理组培养24h后细胞的HIF-1α／和miRNA-21表达高于对照组（P〈0．05）。[结论]人乳腺癌MCF-7细胞可在一定缺氧程度和时间内生长,缺氧诱导细胞凋亡率增加,缺氧能上调HIF-1α、miRNA-21的表达,使之进一步耐受缺氧,其机制可能是上调的miRNA-21通过多个信号通路调控靶基因进而影响癌细胞的增殖及凋亡。     

青蒿琥酯对人乳腺癌MCF-7/TAM细胞的抑制作用

[目的]探讨青蒿琥酯抑制耐三苯氧胺人乳腺癌细胞MCF-7/TAM的增殖及其机制。[方法]采用四甲基偶氮唑蓝（MTT）比色分析法、流式细胞术、免疫细胞化学法技术检测青蒿琥酯作用于MCF-7/TAM细胞后的抑制率、凋亡率、细胞周期及Bcl-2表达变化。[结果]青蒿琥酯对MCF-7/TAM细胞有明显的抑制作用,呈浓度和时间依赖性。作用48h后能诱导细胞凋亡,细胞周期被阻滞于G1、G2期（P〈0.05）。青蒿琥酯处理组Bcl-2表达减弱（P〈0.01）。[结论]青蒿琥酯可抑制MCF-7/TAM细胞的增殖,并诱导其凋亡。     

lncRNA FOXD2-AS1通过靶向miR-506-5p调控宫颈癌细胞增殖与凋亡

[摘要] 目的: 探讨长链非编码RNA（lncRNA）FOXD2-AS1 是否通过靶向miR-506-5p 调控宫颈癌细胞增殖和凋亡。方法:体外培养人宫颈癌细胞系HeLa、Siha、Caski 与正常宫颈细胞株Ect1/E6E7,用qPCR检测细胞中FOXD2-AS1 和miR-506-5p 的表达水平。用脂质体转染技术分别构建抑制FOXD2-AS1 表达和过表达miR-506-5p 的宫颈癌细胞,用MTT实验和流式细胞术检测细胞的增殖和凋亡情况,WB实验检测细胞中增殖相关蛋白CyclinD1、p21 和p27 及凋亡相关蛋白Bcl-2、BAX和cleaved-capase-3的表达。用双荧光素酶报告基因实验验证FOXD2-AS1 是否靶向miR-506-5p,并分析同时抑制FOXD2-AS1 和miR-506-5p 表达对宫颈癌细胞增殖与凋亡的影响。结果：与Ect1/E6E7 细胞比较,宫颈癌HeLa、Siha 和Caski 细胞中FOXD2-AS1 表达水平显著升高,miR-506-5p 表达水平降低（均P<0.01）。抑制FOXD2-AS1 表达可显著抑制宫颈癌细胞中CyclinD1 蛋白和Bcl-2 蛋白表达,并促进p21、p27 和BAX、cleaved-capase-3 蛋白的表达,抑制细胞增殖并促进细胞凋亡（均P<0.01）。过表达miR-506-5p 可显著抑制宫颈癌细胞中CyclinD1 和Bcl-2 蛋白表达,促进p21 和BAX蛋白表达,抑制细胞增殖并促进细胞凋亡（均P<0.01）。双荧光素酶报告基因实验证实宫颈癌细胞中FOXD2-AS1 靶向负调控miR-506-5p 的表达（P<0.01）。抑制miR-506-5p 表达逆转了抑制FOXD2-AS1 表达对宫颈癌细胞增殖和凋亡的作用（P<0.01）。结论: FOXD2-AS1 通过靶向miR-506-5p 的表达调控宫颈癌细胞的增殖和凋亡。     

A lipid-soluble iron chelator alters cell cycle regulatory protein binding in breast cancer cells compared to normal breast cells

The lipid-soluble iron chelator desferri-exochelin (D-Exo) causes reversible cell cycle arrest in normal human mammary epithelial cells (NHMEC) but triggers apoptotic cell death in human breast cancer cells. We studied the effects of iron chelation with D-Exo on cell cycle regulatory proteins in cultures of NHMEC and MCF-7 breast cancer cells. In co-immunoprecipitation studies, D-Exo inhibited binding of cyclins A and E to cyclin dependent kinase 2 (CDK2) in NHMEC, but in MCF-7 cells binding of these cyclins to CDK2 was enhanced. D-Exo treatment markedly increased expression of p53 and increased binding of p21 to CDK2 in the MCF-7 cells but not in NHMEC. Therefore differences in effects of iron chelation on cell cycle protein binding in cancer cells compared to normal cells may trigger apoptosis in cancer cells while normal breast cells are spared.     

siRNA沉默DNMT1对人乳腺癌细胞MCF-7生长的影响

目的 靶向人DNMT1（DNA methyltransferase 1, DNMT1）构建RNA干扰载体,研究其对乳腺癌细胞周期、增殖及凋亡的影响。方法 靶向DNMT1基因设计三条短发夹状RNA(short hairpin RNA, shRNA) 的寡核苷酸片段,构建重组体pGCsi-DNMT1,转染至乳腺癌细胞株MCF-7,定量PCR 法检测DNMT1 mRNA表达水平;流式细胞技术分析细胞周期的变化;MTT 法检测细胞生长情况;Annexin V/PI双染法观察细胞凋亡情况;定量PCR 法分析沉默DNMT1基因后对RASSF1A、p16、p21、p27及ERβ基因表达的影响。结果 在构建的靶向DNMT1的shRNA重组质粒pGCsi-DNMT1中,成功筛选到pGCsi-T3能显著下调DNMT1的表达。实时定量PCR检测结果证实重组质粒pGCsi-DNMT1对乳腺癌MCF-7细胞中DNMT1基因的转录有明显的抑制作用。MCF-7细胞转染后,pGCsi-DNMT1可明显抑制乳腺癌MCF-7细胞的增殖;大量细胞发生凋亡;细胞周期分析可见S期明显减少,而G₁/G₀期细胞显著增加;定量PCR检测到乳腺癌细胞中RASSF1A、p16、p21及ERβ基因mRNA表达水平明显升高,而p27基因表达水平未见明显变化。结论 重组质粒pGCsi DNMT1能特异有效地抑制MCF-7细胞内DNMT1的表达、 抑制细胞增殖、促进细胞凋亡,并可通过抑制DNMT1的活性来解除相关基因启动子区的高度甲基化状态,从而促进肿瘤相关基因的表达,提示DNMT1可作为乳腺癌基因治疗的新靶标。     

Growth inhibition of carcinogen-transformed MCF-12F breast epithelial cells and hormone-sensitive BT-474 breast cancer cells by 1alpha-hydroxyvitamin D5

Several studies have established the active form of vitamin D(3) as an effective tumor-suppressing agent; however, its antitumor activity is achieved at doses that are hypercalcemic in vivo. Therefore, less calcemic vitamin D(3) analog, 1alpha-hydroxy-24-ethyl-cholecalciferol (1alpha[OH]D5), was evaluated for its potential use in breast cancer chemoprevention. Previously, 1alpha(OH)D5 showed anticarcinogenic activity in several in vivo and in vitro models. However, its effects on growth of normal tissue were not known. The present study was conducted to determine the effects of 1alpha(OH)D5 on the growth of normal mouse mammary gland and normal-like human breast epithelial MCF-12F cells and to compare these effects with carcinogen-transformed MCF-12F and breast cancer cells. No significant difference was observed in the growth or morphology of cultured mouse mammary gland and MCF-12F cells in the presence of 1alpha(OH)D5. However, the transformed MCF-12F cells underwent growth inhibition (40-60%, P < 0.05) upon 1alpha(OH)D5 treatment as determined by cell viability assays. Cell cycle analysis showed marked increase (50%) in G-1 phase for cells treated with 1alpha(OH)D5 compared with the controls. Moreover, the percentage of cells in the synthesis (S) phase of cell cycle was decreased by 70% in transformed MCF-12F, BT-474 and MCF-7 cells. The growth arrest was preceded by an increase in expression of cell cycle regulatory proteins p21(Waf-1) and p27(Kip-1). In addition, differential expression studies of parent and transformed MCF-12F cell lines using microarrays showed that prohibitin mRNA was increased 4-fold in the transformed cells. These results indicate that the growth inhibitory effect of 1alpha(OH)D5 was achieved in both carcinogen-transformed MCF-12F and breast cancer cells at a dose that was non-inhibitory in normal-like breast epithelial cells.     

Quinacrine has anticancer activity in breast cancer cells through inhibition of topoisomerase activity

The small molecule Quinacrine (QC, a derivative of 9-aminoacridine), an anti-malaria drug, displays activity against cancer cell lines and can simultaneously suppress nuclear factor-κB (NF-κB) and activate p53 signaling. In this study, we investigated the anticancer mechanism underlying these drug activities in breast cancer cell lines. QC caused a dose-dependent decrease of both anchorage dependent and independent growth of breast cancer cells (MCF-7 and MDA-MB-231) without affecting normal breast epithelial cells (MCF-10A), as evident from clonogenic cell survival, [3-(4,5-dimethylthiazol-2yl-)-2,5-diphenyl tetrazolium bromide] viability, wound healing and soft agar growth. QC activated the proapoptotic marker Bax, PARP cleavage, p53 and its downstream target, p21 (Cip1/Waf1) and downregulated the antiapoptotic marker Bcl-xL and relative luciferase activity of NF-κB in MCF-7 cells. Results of DAPI nuclear staining and FACS analysis show that QC increased apoptosis in a dose-dependent manner. QC caused apoptosis by increasing the cell population in S-phase and simultaneously decreasing the G1 and G2/M populations. A dose-dependent increase of DNA damage as measured by the comet assay was seen in MCF-7 cells after exposure to QC. With regards to the mechanism of DNA damage, we found that QC inhibited topoisomerase activity in MCF-7 cells by increasing the unwinding of supercoiled DNA. Collectively, the results demonstrate that QC has efficient anticancer potential against breast cancer cells via not only an induction of p53 and p21 but also an induction of S phase arrest, DNA damage and inhibition of topoisomerase activity.     

Role of p53/p21(Waf1/Cip1) in the regulation of polyamine analogue-induced growth inhibition and cell death in human breast cancer cells

Intracellular polyamines are absolutely required for cell proliferation and many tumors have abnormal requirements for polyamines. Therefore, the polyamine metabolic pathway represents a rational target for antineoplastic intervention. A number of polyamine analogues act as potent modulators of cellular polyamine metabolism and exhibit encouraging effects against tumor growth in both cell culture and animal studies. In this study we demonstrate that specific polyamine analogues exhibit differential inhibitory action against growth of human breast cancer MCF-7 cells. Treatment of MCF-7 cells with oligoamine analogues and the symmetrically substituted bis(alkyl)-substituted analogue, BENSpm, produced a G1 cell cycle arrest, while the unsymmetrically substituted bis(alkyl)-substituted analogue, CHENSpm, induced a G2/M cell cycle arrest. All four compounds significantly upregulated p53 and p21 expression in MCF-7 cells. Stable transfection of small interfering RNA (siRNA) targeting p53 blocked the expression of p21 induced by the polyamine analogues and significantly reduced polyamine analogue-induced growth inhibition and apoptosis, suggesting that polyamine analogue-induced p21 expression occurs through p53-dependent mechanisms. The effects of analogue exposure on cyclins and cyclin dependent kinases varied with the specific agent used. Expression of p53 siRNA reversed only BENSpm-modulated the cell cycle arrest, suggesting that regulation of cell cycle arrest by p53/p21 induced by polyamine analogues occurs through agent-specific mechanisms. Understanding the mechanism of p53-mediated cellular responses to polyamine analogue may help to improve the therapeutic efficacy of polyamine analogues in human breast cancer.